<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>white-board</title>
  <style>
    body {
      padding-bottom: 240px;
    }
    .container {
      position: relative;
      width: 60%;
      margin: 0 20%;
      padding: 20px 0;
      min-width: 700px;
      display: flex;
      flex-direction: column;
      align-items: center;
    }
    #canvas {
      border: 1px solid #999;
    }
    #canvas:hover {
      cursor: crosshair
    }
    h2 {
      font-size: 18px;
      font-weight: 600;
    }
  </style>
</head>
<body>
  <div class="container">
    <h2>白板示例</h2>
    <canvas id="canvas" width="600" height="400" style="background-color: #fff;"></canvas>
  </div>
</body>
<script src='./canvas.js'></script>
</html>